Vehicle headlamp

ABSTRACT

A headlamp includes a light source, a first auxiliary reflector disposed below a reflector, and a plurality of second auxiliary reflectors disposed on a front side of the first auxiliary reflector at a predetermined interval along a vertical direction. The light source is a line light source extending in a width direction of a vehicle. A sectional shape of a reflecting surface of the first auxiliary reflector taken along a vertical plane that is parallel to the optical axis is a shape of a parabola having an axis line downwardly extending in the forward direction at a predetermined downward inclination angle. A sectional shape of a reflecting surface of each of the second auxiliary reflectors taken along the vertical plane has a shape of a substantially straight line downwardly extending in the forward direction at a downward inclination angle which is smaller than the predetermined downward inclination angle.

The present invention claims priority from Japanese Patent ApplicationNo. 2006-238583 filed on Sep. 4, 2006, the entire content of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a projector-type vehicle headlamp. Morespecifically, the present invention relates to a vehicle headlamp whichforms a low beam light distribution pattern.

DESCRIPTION OF THE RELATED ART

Generally, in a projector-type vehicle headlamp, a projection lens isdisposed on an optical axis extending in a longitudinal direction of thevehicle and a light source is provided behind a rear focal pointthereof, and a light emitted from the light source is reflected by areflector close to the optical axis. In a case of a vehicle headlamp fora low beam, a part of the light reflected by the reflector is shieldedto form a cutoff line of a low beam light distribution pattern by meansof a shade disposed such that an upper edge is positioned at thevicinity of the rear focal point of the projection lens.

JP-A-2001-229715 discloses a projector-type vehicle headlamp in which alight source is a line light source extending in a width direction of avehicle. Specifically, FIG. 5 of JP-A-2001-229715 shows a structure inwhich a first auxiliary reflector which reflects a light emitted fromthe light source in a downward direction and a second auxiliaryreflector which reflects the light reflected by the first auxiliaryreflector in a forward direction are provided separately from thereflector.

When a line light source extending the width direction of the vehicle isemployed as a light source of the projector-type vehicle headlamp, it ispossible to easily obtain a structure of a lamp in which a light sourcebulb is inserted and fixed to a reflector from a side. Consequently, thelamp can be downsized by reducing a size of the lamp in a front-and-reardirection.

Moreover, when a structure including the first and second auxiliaryreflectors is employed, it is possible to increase a luminous fluxutilization ratio to the light emitted from the light source, therebymaintaining a sufficient brightness of a low beam light distributionpattern.

However, in the vehicle headlamp disclosed in FIG. 5 ofJP-A-2001-229715, a reflecting surface of the first auxiliary reflectoris formed in a shape of an ellipsoid of revolution in which a point inthe vicinity of the light source is set to be a first focal point and apoint positioned therebelow is set to be a second focal point, and areflecting surface of the second auxiliary reflector is formed in ashape of a paraboloid of revolution in which the second focal point isset to be a focal point. For this reason, there are the followingproblems.

More specifically, in the vehicle headlamp, a light source image formedin the second focal point of the ellipsoid of revolution is set to be afalse light source to control a reflected light through the secondauxiliary reflector. However, a shape of the false light source isentirely different from that of an original line light source. For thisreason, there is a problem in that the control of the reflected lightcannot be carried out finely.

SUMMARY OF THE INVENTION

An aspect of the invention provides a projector-type vehicle headlampoperable to form a bright low beam light distribution pattern with highprecision, while reducing a size of the lamp in a front-and-reardirection direction.

According to one or more aspects of the invention, a vehicle headlampincludes:

a projection lens disposed on an optical axis extending in alongitudinal direction of a vehicle;

a light source disposed on a rear side of a rear focal point of theprojection lens;

a reflector which forwardly reflects a light emitted from the lightsource toward the optical axis;

a shade disposed such that an upper edge of the shade is positioned inthe vicinity of the optical axis near the rear focal point, wherein theshade shields a part of the light reflected by the reflector, and formsa cutoff line of a low beam light distribution pattern;

a first auxiliary reflector disposed below the reflector, and downwardlyreflects the light emitted from the light source in a forward direction;and

a plurality of second auxiliary reflectors disposed on a front side ofthe first auxiliary reflector at a predetermined interval along avertical direction, and forwardly reflect the light reflected by thefirst auxiliary reflector.

The light source may be a line light source extending in a widthdirection of the vehicle. A sectional shape of a reflecting surface ofthe first auxiliary reflector taken along a vertical plane that isparallel to the optical axis is a shape of a parabola, the parabolahaving a focal point in the vicinity of the light source and an axisline downwardly extending in the forward direction at a predetermineddownward inclination angle with respect to the optical axis. A sectionalshape of a reflecting surface of each of the second auxiliary reflectorstaken along the vertical plane has a shape of a substantially straightline downwardly extending in the forward direction at a downwardinclination angle which is smaller than the predetermined downwardinclination angle.

A specific structure of the light source is not particularly restrictedas long as the light source is a line light source that extends in awidth direction of a vehicle. For example, the light source may be adischarging light emitting portion of a discharge bulb or a filament ofa halogen bulb. Moreover, the light source may be positioned either onthe optical axis or out of the optical axis.

A sectional shape of the reflecting surface of the first auxiliaryreflector taken along a vertical plane which is orthogonal to theoptical axis is not particularly restricted as long as a sectional shapetaken along a vertical plane which is parallel to the optical axis is ashape of a parabola having a focal point in the vicinity of the lightsource and an axis line downwardly extending in the forward direction ata predetermined downward inclination angle with respect to the opticalaxis.

A specific arrangement and the number of the second auxiliary reflectorsis not particularly restricted as long as they are arranged at aninterval in a vertical direction. A specific value of the downwardinclination angle of the reflecting surface of the second auxiliaryreflector is not particularly restricted as long as a sectional shapetaken along the vertical plane which is parallel to the optical axis isa shape of an almost straight line downwardly extending in the forwarddirection at a downward inclination angle that is smaller than thepredetermined downward inclination angle. Furthermore, a sectional shapeof the second auxiliary reflectors taken along a vertical plane which isorthogonal to the optical axis is not particularly restricted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing a vehicle headlamp according to a firstexemplary embodiment of the invention;

FIG. 2 is a sectional view taken along a II-II line in FIG. 1;

FIG. 3 is a sectional view taken along a III-III line in FIG. 1;

FIG. 4 is a perspective view showing a low beam light distributionpattern formed on a virtual vertical screen disposed 25 m ahead of alamp by a light irradiated from the vehicle headlamp in a forwarddirection;

FIGS. 5A to 5C are views for explaining a process for forming threeauxiliary light distribution patterns, each forming a part of the lowbeam light distribution pattern, by using the virtual vertical screen;and

FIG. 6 is a front view illustrating a second exemplary embodiment.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the invention will be explainedwith reference to the drawings. The following exemplary embodiments donot limit the scope of the invention.

As shown in FIGS. 1 to 3, a vehicle headlamp 10 according to the firstexemplary embodiment is of a projector-type, and irradiates a light toform a low beam light distribution pattern, and is used in anincorporating state in a lamp body (not shown) so as to freely regulatean optical axis.

The vehicle headlamp 10 includes a projection lens 12, a light sourcebulb 14, a reflector 16, a shade 18, a lens holder 20, a bracket 22, afirst auxiliary reflector 32, a plurality of second auxiliary reflectors34A, 34B and 34C (three in the first exemplary embodiment), a thirdauxiliary reflector 36, a fourth auxiliary reflector 38 and a diffusionlens 40, and has an optical axis Ax extending in a longitudinaldirection of the vehicle. The vehicle headlamp 10 is disposed in a statein which the optical axis Ax is extended in a downward direction byapproximately 0.5 to 0.6 degree with respect to the longitudinaldirection of the vehicle in a stage in which the regulation of theoptical axis is completed.

The projection lens 12 is disposed on the optical axis Ax and projectsan image on a focal plane including a rear focal point F as an invertedimage on a vertical virtual screen disposed ahead of a lamp. Theprojection lens 12 according to the first exemplary embodiment is aFresnel lens formed of a synthetic resin in which a forward surface in aplano-convex aspherical lens having a forward surface to be a convexsurface and a rear surface to be a plane is formed like a step of aconcentric circle. An inclination angle of each annular step portion 12a is set to be approximately 10 to 15 degrees (for example, 12 degrees).The projection lens 12 is supported by the annular lens holder 20, andthe lens holder 20 is fixed to the bracket 22 at rear ends of a pair ofleft and right leg portions 20 a extended rearward from both sideportions thereof.

The light source bulb 14 may be a discharge bulb such as a metal halidebulb in which a discharging light emitting portion serves as a lightsource 14 a, and the light source 14 a may be a line light sourceextending along a bulb center axis Ax1. The light source bulb 14 isinserted and fixed into a bulb inserting hole 22 a of the bracket 22from a right side (a left side seen from a front of the lamp and soforth) on a rear side of the rear focal point F of the projection lens12 below the optical axis Ax. The insertion and fixation is carried outso as to place a central position of the light source 14 a (that is, acentral position between ignition electrodes on the bulb center axisAx1) under the optical axis Ax in a state in which the bulb center axisAx1 is set to be extended in a horizontal direction in a vertical planewhich is orthogonal to the optical axis Ax (that is, a state in whichthe bulb center axis Ax1 is set to be extended in a width direction of avehicle).

The reflector 16 is disposed so as to cover the light source 14 a on anupper-rear side, and is fixed to the bracket 22 in both side edgeportions thereof. The reflector 16 has a reflecting surface 16 a forreflecting a light emitted from the light source 14 a close to theoptical axis Ax in a forward direction. In the reflecting surface 16 a,a sectional shape including a straight light connecting a centralposition of the light source 14 a and the rear focal point F of theprojection lens 12 is set to take an elliptical shape, and furthermore,an eccentricity thereof is set to be gradually increased from a verticalsection toward a section which is inclined to both of left and rightsides. As shown in FIGS. 2 and 3, consequently, the light emitted fromthe light source 14 a and reflected by the reflecting surface 16 a isalmost converged in the vicinity of the rear focal point F in thevertical section, and furthermore, a converging position thereof ismoved forward in a horizontal section thereof.

The shade 18 is disposed between the projection lens 12 and thereflector 16 and is fixed to the bracket 22 in both side edge portionsthereof. The shade 18 is formed to take a shape of an almost circulararc along the rear focal plane of the projection lens 12 such that anupper edge 18 a passes through the rear focal point F of the projectionlens 12. Consequently, the shade 18 shields a part of the lightreflected by the reflecting surface 16 a of the reflector 16 and removesmost of an upward light emitted from the projection lens 12 in a forwarddirection. The upper edge 18 a of the shade 18 is formed such that aregion on a left side of the optical axis Ax is extended horizontally ina leftward direction from the optical axis Ax, and a region on a rightside of the optical axis Ax is extended formed obliquely downward in arightward direction from the optical axis Ax (e.g., downward by 15degrees) and is then extended horizontally in the rightward direction.

The first auxiliary reflector 32 is disposed below the reflector 16, anddownwardly reflects the light emitted from the light source 14 a towarda forward direction.

A sectional shape of a reflecting surface 32 a of the first auxiliaryreflector 32, taken along a vertical plane which is parallel to theoptical axis Ax, has a shape of a parabola having a focal point at alight emitting center of the light source 14 a and an axis line Ax2downwardly extending in the forward direction at a predetermineddownward inclination angle with respect to the optical axis Ax (e.g.,approximately 40 degrees) as an axis thereof. The reflecting surface 32a is a paraboloid of revolution having the axis line Ax2 as a centeraxis. Consequently, the light emitted from the light source 14a isdownwardly reflected in the forward direction as a parallel light havingno spreading in a horizontal direction and in a vertical direction.

The first auxiliary reflector 32 is formed such that a front edge of thereflecting surface 32 a is extended to a position placed almost underthe light source 14 a in a vertical plane including the optical axis Ax,and a pair of left and right vertical walls 32 b are formed onrespective side edge portions. The first auxiliary reflector 32 and thebracket 22 are formed in a one-piece structure.

All of the three second auxiliary reflectors 34A, 34B and 34C aredisposed on a front side of the first auxiliary reflector 32, and eachof the second auxiliary reflectors 34A, 34B and 34C reflect the lightemitted from the light source 14 a and reflected by the first auxiliaryreflector 32 in a forward direction.

The three second auxiliary reflectors 34A, 34B and 34C are disposed atalmost equal intervals in a vertical direction. The second auxiliaryreflector 34A positioned at a lowermost stage and the first auxiliaryreflector 32 are formed in a one-piece structure, and the other twosecond auxiliary reflectors 34B and 34C are fixed to the respectivevertical walls 32 b of the first auxiliary reflector 32 on both of theleft and right side edge portions.

Reflecting surfaces 34Aa, 34Ba and 34Ca of the second auxiliaryreflectors 34A, 34B and 34C are respectively inclined. Morespecifically, a sectional shape of each of the reflecting surfaces 34Aa,34Ba and 34Ca taken along a vertical plane which is parallel to theoptical axis Ax is has a shape of a straight line downwardly extendingin the forward direction at a downward inclination angle which issmaller than a downward inclination angle of the axis line Ax2. Asectional shape of each of the reflecting surfaces 34Aa, 34Ba and 34Cataken along a vertical plane which is orthogonal to the optical axis Axhas a shape of a straight line extending in a horizontal direction.

A shape of a rear edge of the reflecting surface 34Aa of the secondauxiliary reflector 34A positioned at a lowermost stage has a shape of acurved line extending along the front edge of the reflecting surface 32a of the first auxiliary reflector 32. Shapes of rear edges of thereflecting surfaces 34Ba and 34Ca of the other two second auxiliaryreflectors 34B and 34C also have the shape of the rear edge of thereflecting surface 34Aa of the second auxiliary reflector 34A. Positionsof the two second auxiliary reflectors 34B and 34C in a front-and-reardirection are aligned to the position of the rear edge of the reflectingsurface 34Aa of the second auxiliary reflector 34A. Consequently, thelight emitted from the light source 14 a and reflected as a parallellight, which is downwardly directed toward the forward direction, by thefirst auxiliary reflector 32 is also incident on all of the reflectingsurfaces 34Aa, 34Ba and 34Ca of the three second auxiliary reflectors34A, 34B and 34C. The front edges of the second auxiliary reflectors34A, 34B and 34C are positioned almost under the projection lens 12 andare formed like a straight line in a horizontal direction.

The downward inclination angles of the reflecting surfaces 34Aa, 34Baand 34Ca of the three second auxiliary reflectors 34A, 34B and 34C areset to have values which are a little greater than a half of thedownward inclination angle of the axis line Ax2. The downwardinclination angle of the reflecting surface 34Aa of the second auxiliaryreflector 34A positioned at the lowermost stage is set to have aslightly greater value than a half value of the downward inclinationangle of the axis line Ax2, the downward inclination angle of thereflecting surface 34Ba of the second auxiliary reflector 34B positionedat a middle stage is set to have a slightly greater value, and thedownward inclination angle of the reflecting surface 34Ca of the secondauxiliary reflector 34C positioned at an uppermost stage is set to havea further slightly greater value.

The downward inclination angles of the three reflecting surfaces 34Aa,34Ba and 34Ca are delicately changed for the following reason.

As shown in FIG. 2, the light emitted from the light source 14 a andreflected by the first auxiliary reflector 32 is incident as a parallellight on the respective second auxiliary reflectors 34A, 34B and 34C.The light reflected by the first auxiliary reflector 32 becomes a bundleof rays having spreading in a vertical direction which corresponds to avertical width of the light source 14 a. Therefore, the light reflectedby the respective second auxiliary reflectors 34A, 34B and 34C, whichregularly reflect the bundle of rays, also becomes a bundle of rayshaving the spreading in the vertical direction which corresponds to thevertical width of the light source 14 a. More specifically, the lightreflected by an upper region of the reflecting surface 32 a of the firstauxiliary reflector 32 becomes a bundle of rays having relatively largespreading in the vertical direction and is reflected by the secondauxiliary reflector 34C positioned at the uppermost stage. Accordingly,the downward inclination angle of the reflecting surface 34Ca of thesecond auxiliary reflector 34C is set to have a relatively large angle.On the other hand, a light reflected by a lower region of the reflectingsurface 32 a of the first auxiliary reflector 32 becomes a bundle ofrays having relatively small spreading in the vertical direction and isreflected by the second auxiliary reflector 34A positioned at alowermost stage. Accordingly, the downward inclination angle of thereflecting surface 34Aa of the second auxiliary reflector 34A is set tohave a relatively small angle. As for the second auxiliary reflector 34Bpositioned at a middle stage, the downward inclination angle of thereflecting surface 34Ba is set to have an intermediate value betweenthose of the second auxiliary reflectors 34A and 24C. According to sucha configuration, a position of the larger light source image formed bythe light reflected by the second auxiliary reflector 34C can bedownwardly displaced as compared with a position of a smaller lightsource image formed by the light reflected by the second auxiliaryreflector 34A positioned on a lower stage side. Thus, the direction ofthe upper edge of the bundle of the light reflected by each of thesecond auxiliary reflectors 34A, 34B and 34C is set to be coincidentwith a direction parallel with respect to the optical axis Ax.

In the first exemplary embodiment, the second auxiliary reflector 34Cpositioned at the uppermost stage is formed such that both left andright regions 34CaL and 34CaR are set to have slightly smaller values ofthe downward inclination angles than a central region 34CaC of thereflecting surface 34Ca, whereby a light reflected by the both left andright regions 34CaL and 34CaR is reflected more upwardly than a lightreflected by the central region 34CaC.

The light reflected by both the left and right regions 34CaL and 34CaRis reflected relatively upward for the following reason.

A light reflected by the upper region of the reflecting surface 32 a ofthe first auxiliary reflector 32 is incident on the reflecting surface34Ca of the second auxiliary reflector 34C which is positioned at theuppermost stage. In the upper region of the reflecting surface 32 a,however, a difference between a distance from the light source 14 a to apoint at a central region and distances from the light source 14 a topoints at respective side regions in the horizontal direction isrelatively large compared with the lower regions of the reflectingsurface 32 a. For this reason, especially with regard to a light sourceimage formed by the light reflected by the reflecting surface 34Ca ofthe second auxiliary reflector 34C positioned at the uppermost stage,light source images formed by light reflected by respective side regions34CaL and 34CaR are smaller than a light source image formed by a lightreflected by the central region 34CaC. Thus, at least for the reflectingsurface 34Ca of the second auxiliary reflector 34C positioned at theuppermost stage, the left and right regions 34CaL and 34CaR are formedso as to reflect light relatively upward as compared with that in thecentral region 34CaC, whereby the positions of the upper edges arealigned between the large light source image formed by the lightreflected by the central region 34CaC and the small light source imageformed by the light reflected by each of the left and right regions34CaL and 34CaR which are positioned on both of the left and rightsides.

The third auxiliary reflector 36 is disposed in front of the lightsource 14 a in order to effectively utilize a light emitted toward aforward direction from the light source 14 a. A reflecting surface 36 aof the third auxiliary reflector 36 is a spherical surface having itscenter at the central position of the light source 14 a, and reflectsback the light forwardly emitted from the light source 14 a toward thelight source 14 a and causes the light to be incident on the reflector16 and the first auxiliary reflector 32. The third auxiliary reflector36 and the shade 18 are formed in a one-piece structure.

The fourth auxiliary reflector 38 is disposed above the shade 18. Areflecting surface 38 a of the fourth auxiliary reflector 38 is aspherical surface having its center at the central position of the lightsource 14 a, and reflects back a light that is upwardly directed fromthe light source 14 a in the forward direction and passed between thereflector 16 and the shade 18 back toward the light source 14 a, andcauses the light to be incident on the first auxiliary reflector 32. Thethird auxiliary reflector 36 is fixed to the reflector 16 and thebracket 22.

In a position placed almost under the projection lens 12 (that is, inthe vicinity of the forward parts of the three second auxiliaryreflectors 34A, 34B and 34C), the diffusion lens 40 is disposed to coverthe three second auxiliary reflectors 34A, 34B and 34C and the firstauxiliary reflector 32 from a forward side and is fixed to both of thevertical walls 32 b of the first auxiliary reflector 32 in both sideedge portions thereof.

A plurality of diffusion lens portions 40 s is formed on a rear face ofthe diffusion lens 40 in a form of vertical stripes. By the diffusionlens portions 40 s, a parallel light reflected regularly by each of thesecond auxiliary reflectors 34A, 34B and 34C is forwardly irradiated asa light to be diffused in a horizontal direction.

FIG. 4 is a perspective view showing a low beam light distributionpattern PL which is formed on a virtual vertical screen disposed 25 mahead of a lamp by a light irradiated forward from the vehicle headlamp10 according to the first exemplary embodiment.

The low beam light distribution pattern PL is formed as a syntheticlight distribution pattern of a basic light distribution pattern P0 andthree auxiliary light distribution patterns PA, PB and PC.

The basic light distribution pattern P0 is a light distribution patterntaking a basic shape of the low beam light distribution pattern PL andis formed by a light reflected by the reflector 16.

The basic light distribution pattern P0 is a low beam light distributionpattern which has a left light distribution, and has cutoff lines CL1and CL2 at an upper edge thereof. The cutoff lines CL1 and CL2 areformed as an inverted projection image of the upper edge 18 a of theshade 18. The cutoff line CL1 on an opposing lane side is formed to beextended horizontally and the cutoff line CL2 on a self-lane side isformed to be raised slightly upward and obliquely from an H-H line (thatis, a horizontal line passing through H-V to be a vanishing point in afront direction of the lamp) at a predetermined angle (for example, 15degrees) from the cutoff line CL1 on the opposing lane side and to bethen extended horizontally.

In the basic light distribution pattern P0, an elbow point E to be anintersection point of the cutoff line CL1 on the opposing lane side anda V-V line (that is, a vertical line passing through H-V) is positionedbelow H-V at approximately 0.5 to 0.6 degree. The reason is that theoptical axis Ax is extended in a downward direction by approximately 0.5to 0.6 degree with respect to the longitudinal direction of the vehicle.

The basic light distribution pattern P0 is formed as a comparativelysmall light distribution pattern for the following reason.

In the projection lens 12 which may be a Fresnel lens, when an angle ofemission from the projection lens 12 is increased, a light is easilyincident on the annular step portion 12 a on the surface at the forwardside thereof. However, the annular step portion 12 a is an opticallyineffective portion. For this reason, the basic light distributionpattern P0 is set to be a comparatively small light distribution patternsuch that the angle of light emission from the projection lens 12 is notincreased greatly. Moreover, the projection lens 12 is formed of asynthetic resin. Therefore, in consideration of the fact that theprojection lens 12 might be deformed by heat when the light reflected bythe reflector 16 is converged in the vicinity of the projection lens 12,the basic light distribution pattern P0 is set to be a comparativelysmall light distribution pattern to converge the light reflected by thereflector 16 in a position placed apart from the projection lens 12 in arearward direction. Consequently, a heat deformation is prevented frombeing generated.

The three auxiliary light distribution patterns PA, PB and PC areadditionally formed to reinforce a brightness in the basic lightdistribution pattern P0 and diffusion regions on both of left and rightsides thereof in the low beam light distribution pattern PL.

The auxiliary light distribution pattern PA is formed by the lightemitted from the light source 14 a, reflected sequentially by the firstauxiliary reflector 32 and the second auxiliary reflector 34A in thelowermost stage, transmitted through the diffusion lens 40 and diffusedand irradiated in the forward direction, and is formed as a horizontallight distribution pattern having a small vertical width and a muchgreater lateral diffusion angle than that of the basic lightdistribution pattern P0.

The auxiliary light distribution pattern PB is formed by the lightemitted from the light source 14 a, reflected sequentially by the firstauxiliary reflector 32 and the second auxiliary reflector 34B in themiddle stage, transmitted through the diffusion lens 40 and diffused andirradiated in the forward direction, and is formed as a horizontal lightdistribution pattern having a greater vertical width and a slightlygreater lateral diffusion angle than those of the auxiliary lightdistribution pattern PA.

The auxiliary light distribution pattern PC is formed by the lightemitted from the light source 14 a, reflected sequentially by the firstauxiliary reflector 32 and the second auxiliary reflector 34C in theuppermost stage, transmitted through the diffusion lens 40 and diffusedand irradiated in the forward direction, and is formed as a horizontallight distribution pattern having a further greater vertical width and aslightly greater lateral diffusion angle than those of the auxiliarylight distribution pattern PB. A part of the auxiliary lightdistribution pattern PC is formed by two horizontal light distributionpatterns PCL and PCR. The two lateral light distribution patterns PCLand PCR are formed at slightly smaller lateral diffusion angles than theauxiliary light distribution pattern PC.

All of the three auxiliary light distribution patterns PA, PB and PChave upper edges formed to be extended in an almost horizontal directionin positions on almost the same level as the cutoff line CL1 on anopposing lane side of the basic light distribution pattern P0. The twohorizontal light distribution patterns PCL and PCR forming a part of theauxiliary light distribution pattern PC also have upper edges formed tobe extended in the almost horizontal direction in the positions onalmost the same level as the cutoff line CL1 on the opposing lane sideof the basic light distribution pattern P0.

FIG. 5 is a view for explaining a process for forming each of theauxiliary light distribution patterns PA, PB and PC by using the virtualvertical screen.

As shown in FIG. 5A, the auxiliary light distribution pattern PA isformed by diffusing the auxiliary light distribution pattern PA₀ towardboth left and right sides. Assuming that the diffusion lens 40 is notpresent, the auxiliary light distribution pattern PA₀ is formed by thelight emitted from the light source 14 a, reflected sequentially by thefirst auxiliary reflector 32 and the second auxiliary reflector 34A inthe lowermost stage and diffused and irradiated in the forwarddirection.

The auxiliary light distribution pattern PA₀ is formed by the lightreflected by a lower region in the reflecting surface 32 a of the firstauxiliary reflector 32. All of light source images formed by lightsreflected from respective points in the reflecting surface 34Aa of thesecond auxiliary reflector 34A are images that are close to the shape ofthe light source 14 a (the horizontal line light source) and are small.Therefore, the auxiliary light distribution pattern PA₀ formed by theinnumerable light source images also has an external shape which ishorizontal, small and almost rectangular.

The upper edge of the auxiliary light distribution pattern PA₀ ispositioned on almost the same level as the cutoff line CL1 on theopposing lane side of the basic light distribution pattern P0. Thereason is that the downward inclination angle of the reflecting surface34Aa is set such that the direction of the upper edge of the bundle ofrays of the light reflected by the second auxiliary reflector 34A iscoincident with a direction parallel to the optical axis Ax.

As shown in FIG. 5B, the auxiliary light distribution pattern PB isformed by diffusing the auxiliary light distribution pattern PB₀ towardboth left and right sides. Assuming that the diffusion lens 40 is notpresent, the auxiliary light distribution pattern PB₀ is formed by thelight emitted from the light source 14 a, reflected sequentially by thefirst auxiliary reflector 32 and the second auxiliary reflector 34B inthe middle stage and diffused and irradiated in the forward direction.

The auxiliary light distribution pattern PB₀ is formed by the lightreflected from a central region in a vertical direction in thereflecting surface 32 a of the first auxiliary reflector 32. All oflight source images formed by lights reflected from respective points inthe reflecting surface 34Ba of the second auxiliary reflector 34B areimages which are comparatively close to the shape of the light source 14a (the horizontal line light source) and are slightly large. Therefore,the auxiliary light distribution pattern PB₀ formed by the innumerablelight source images also has an almost rectangular external shape whichis horizontal and has a larger size and a lower aspect ratio than thoseof the auxiliary light distribution pattern PA₀.

The upper edge of the auxiliary light distribution pattern PB₀ ispositioned on almost the same level as the cutoff line CL1 on theopposing lane side of the basic light distribution pattern P0. Thereason is that the downward inclination angle of the reflecting surface34Ba is set such that the direction of the upper edge of the bundle ofrays of the light reflected by the second auxiliary reflector 34B iscoincident with a direction parallel to the optical axis Ax.

As shown in FIG. 5C, the auxiliary light distribution pattern PC isformed by diffusing the auxiliary light distribution pattern PC₀ towardboth left and right sides. Assuming that the diffusion lens 40 is notpresent, the auxiliary light distribution pattern PC₀ is formed by thelight emitted from the light source 14 a, reflected sequentially by thefirst auxiliary reflector 32 and the second auxiliary reflector 34C inthe uppermost stage and diffused and irradiated in the forwarddirection.

The auxiliary light distribution pattern PC₀ is formed by the lightreflected from an upper region in the reflecting surface 32 a of thefirst auxiliary reflector 32. All of light source images formed bylights reflected from respective points in the reflecting surface 34Caof the second auxiliary reflector 34C are images which are comparativelyclose to the shape of the light source 14 a (the horizontal line lightsource) and are large. Therefore, the auxiliary light distributionpattern PC₀ formed by the innumerable light source images also has analmost rectangular external shape which is horizontal and has a largersize and a lower aspect ratio than those of the auxiliary lightdistribution pattern PB₀.

The upper edge of the auxiliary light distribution pattern PC₀ ispositioned on almost the same level as the cutoff line CL1 on theopposing lane side of the basic light distribution pattern P0. Thereason is that the downward inclination angle of the reflecting surface34Ca is set such that the direction of the upper edge of the bundle ofrays of the light reflected by the second auxiliary reflector 34C iscoincident with a direction parallel to the optical axis Ax.

A part of the auxiliary light distribution pattern PC₀ is formed by twolight distribution patterns PCL₀ and PCR₀ formed by lights reflectedfrom both of the left and right regions 34CaL and 34CaR in thereflecting surface 34Ca of the second auxiliary reflector 34C. The twolight distribution patterns PCL₀ and PCR₀ are much smaller than theauxiliary light distribution pattern PC₀ and are inclined to ahorizontal direction. The reason is as follows. More specifically, inthe reflecting surface 34Ca of the second auxiliary reflector 34C onwhich the light reflected by the upper region in the reflecting surface32 a of the first auxiliary reflector 32 is incident, the light sourceimages formed by the lights reflected from both of the left and rightregions 34CaL and 34CaR are much smaller than the light source imagesformed by the light reflected from the central region 34CaC and thelight source 14 a (the horizontal line light source) forms an inclinedimage as described above.

On the assumption that the downward inclination angles of both of theleft and right regions 34CaL and 34CaR are equal to the downwardinclination angle of the central region 34CaC, the two lightdistribution patters PCL₀ and PCR₀ are formed in positions shown in abroken line in FIG. 5C. Actually, the downward inclination angles ofboth of the left and right regions 34CaL and 34CaR are set to haveslightly smaller values than the downward inclination angle of thecentral region 34CaC. For this reason, the light distribution patternsPCL₀ and PCR₀ are formed in positions shown in a solid line which arecorrespondingly displaced in an upward direction. The two lightdistribution patterns PCL₀ and PCR₀ are diffused in a horizontaldirection by means of the diffusion lens 40 so that two lateral lightdistribution patterns PCL and PCR having upper edges positioned onalmost the same level as the cutoff line CL1 on the opposing lane sideof the basic light distribution pattern P0 are formed as shown in asolid line in place of the broken line in FIG. 5C.

As described above in detail, the projector-type vehicle headlamp 10according to the first exemplary embodiment has the shade 18 and thelight source 14 a which is a line light source extending in the widthdirection of the vehicle. Therefore, it is possible to easily have alamp structure in which the light source bulb 14 is inserted and fixedinto the reflector 16 from the side thereof. Consequently, it ispossible to reduce the size of the lamp in a front-and-rear direction,thereby causing the lamp to be compact.

In the vehicle headlamp 10 according to the first exemplary embodiment,the first auxiliary reflector 32 which downwardly reflects the lightemitted from the light source 14 a in the forward direction is disposedbelow the reflector 16, and a plurality of (three according to the firstexemplary embodiment) second auxiliary reflectors 34A, 34B and 34C,which forwardly reflect the light emitted from the light source 14 a andreflected by the first auxiliary reflector 32, are disposed on a frontside of the first auxiliary reflector 32. Therefore, it is possible toform the low beam light distribution pattern PL as a synthetic lightdistribution pattern in which the auxiliary light distribution patternsPA, PB and PC formed by the lights irradiated from the first auxiliaryreflector 32 and the three second auxiliary reflectors 34A, 34B and 34Care superposed on the basic light distribution pattern P0 formed by thelight irradiated through the reflector 16 and the projection lens 12.Consequently, it is possible to increase a luminous flux utilizationratio to the light emitted from the light source 14 a, therebymaintaining the brightness of the low beam light distribution pattern PLsufficiently.

In the vehicle headlamp 10 according to the first exemplary embodiment,the sectional shape of the reflecting surface 32 a of the firstauxiliary reflector 32 taken along the vertical plane which is parallelto the optical axis Ax in is has a shape of a parabola having its focalpoint at the center of the light source 14 a and the axis line Ax2downwardly extending in the forward direction at a predetermineddownward inclination angle with respect to the optical axis Ax as itsaxis. Therefore, the light emitted from the light source 14 a andreflected by the first auxiliary reflector 32 becomes the parallel lightwhich is downwardly directed in the forward direction in the verticalplane. The light source 14 a, which is a line light source extending inthe width direction of the vehicle, is an almost point light source inthe vertical plane that is parallel to the optical axis Ax. Therefore,the light emitted from the light source 14 a and reflected by the firstauxiliary reflector 32 is incident as a parallel light which rarely hasspreading in the vertical direction on each of the three secondauxiliary reflectors 34A, 34B and 34C disposed at a predeterminedinterval in the vertical direction.

In the second auxiliary reflectors 34A, 34B and 34C, the sectionalshapes of the reflecting surface 34Aa, 34Ba and 34Ca taken along thevertical planes have the shape of the straight line downwardly extendingin the forward direction at a smaller downward inclination angle thanthe predetermined downward inclination angle. Therefore, the lightemitted from the light source 14 a and reflected by the first auxiliaryreflector 32 is regularly reflected by the second auxiliary reflectors34A, 34B and 34C, and is forward irradiated as a parallel light whichrarely has spreading in the vertical direction.

The light emitted from the light source 14 a is changed into theparallel light through the first auxiliary reflector 32 and is regularlyreflected by the second auxiliary reflectors 34A, 34B and 34C in thevertical plane which is parallel to the optical axis Ax. Consequently,it is possible to finely control the lights reflected by the firstauxiliary reflector 32 and the second auxiliary reflectors 34A, 34B and34C. More specifically, by properly setting the downward inclinationangles of the reflecting surfaces of the second auxiliary reflectors34A, 34B and 34C, it is possible to form the auxiliary lightdistribution patterns PA, PB and PC along the cutoff line CL1 on theopposing lane side of the basic light distribution pattern P0.

When a combination of the first auxiliary reflector 32 and the secondauxiliary reflectors 34A, 34B and 34C irradiate the light emitted fromthe light source 14 a as the diffusion light, which is diffused in thehorizontal direction, it is possible to form the auxiliary lightdistribution pattern PA, PB and PC as the horizontal light distributionpatterns. On the other hand, when the first auxiliary reflector 32 andthe second auxiliary reflectors 34A, 34B and 34C forwardly irradiate thelight emitted from the light source 14 a as an almost parallel lightwhich is not diffused in the horizontal direction, it is possible toform the auxiliary light distribution pattern PA, PB and PC as collectedlight distribution patterns.

According to the first exemplary embodiment, the diffusion lens 40,which diffuses the light reflected by the three second auxiliaryreflectors 34A, 34B and 34C in the horizontal direction, is disposed ona front side of the second auxiliary reflectors 34A, 34B and 34C. Thus,even if the first auxiliary reflector 32 and the second auxiliaryreflectors 34A, 34B and 34C do not have a light diffusing function inthe horizontal direction, it is possible to form the horizontalauxiliary light distribution patterns PA, PB and PC. Consequently, it ispossible to easily form the reflecting surface 32 a of the firstauxiliary reflector 32 and the reflecting surfaces 34Aa, 34Ba and 34Caof the second auxiliary reflectors 34A, 34B and 34C with high precision.

According to the first exemplary embodiment, it is possible to reducethe size of the lamp in the front-and-rear direction, and theprojector-type vehicle headlamp 10 forms the bright low beam lightdistribution pattern PL with high precision.

In addition, in the vehicle headlamp 10 according to the first exemplaryembodiment, the light that is forwardly emitted from the light source 14a is reflected back toward the light source 14 a by the third auxiliaryreflector 36, and becomes incident on the reflector 16 and the firstauxiliary reflector 32. The light forwardly emitted from the lightsource 14 a is reflected back toward the light source 14 a by the fourthauxiliary reflector 38 and becomes incident on the first auxiliaryreflector 32. Therefore, it is possible to correspondingly increase thebrightness of each of the basic light distribution pattern P0 and theauxiliary light distribution patterns PA, PB and PC. Consequently, thelow beam light distribution pattern PL can be made brighter.

In the vehicle headlamp 10 according to the first exemplary embodiment,the projection lens 12 may be a Fresnel lens. Therefore, it is possibleto reduce the thickness of the projection lens 12. Consequently, it ispossible to promote a reduction in the size of the lamp in afront-and-rear direction still more. In a case in which is a Fresnellens is employed as the projection lens 12, the annular step portion 12a is an optically ineffective portion. Therefore, it is difficult toform the basic light distribution pattern having a large diffusion. Inaddition, in the projection lens 12 formed of a synthetic resinaccording to the first exemplary embodiment, it is difficult to form thebasic light distribution pattern having the large diffusion also inrespect of a prevention of heat deformation. Therefore, it isparticularly effective to form the horizontal auxiliary lightdistribution patterns PA, PB and PC along the cutoff line CL1 on theopposing lane side of the basic light distribution pattern P0. Morespecifically, the auxiliary light distribution patterns PA, PB and PCare formed such that the upper edges are extended on almost the samelevel as the cutoff line CL1 on the opposing lane side at both of theleft and right sides of the basic light distribution pattern P0.Consequently, it is possible to enhance a distance of visibility on bothof the left and right sides of the forward road surface of the vehicle,thereby improving a running safety in a turning operation.

In the vehicle headlamp 10 according to the first exemplary embodiment,the reflecting surface 32 a of the first auxiliary reflector 32 isformed in a shape of a paraboloid of revolution having the axis line Ax2as its center axis. Therefore, the light reflected by the firstauxiliary reflector 32 is a parallel light having no spreading in thehorizontal direction and in the vertical direction. The reflectingsurfaces 34Aa, 34Ba and 34Ca of the second auxiliary reflectors 34A, 34Band 34C are flat. Therefore, the light reflected by the first auxiliaryreflector 32 can be directly reflected regularly as a parallel light byeach of the second auxiliary reflectors 34A, 34B and 34C. Consequently,it is possible to easily carry out a design of a light distribution withhigh precision.

In addition, regarding the downward inclination angles of the straightlines forming the sectional shapes of the reflecting surfaces 34Aa, 34Baand 34Ca of the three second auxiliary reflectors 34A, 34B and 34C takenalong the vertical planes, the downward inclination angle of thereflecting surface 34Ca of the second auxiliary reflector 34C positionedat the uppermost stage is greater than that of the reflecting surface34Ba of the second auxiliary reflector 34B positioned at the middlestage, and the downward inclination angle of the reflecting surface 34Baof the second auxiliary reflector 34B positioned at the middle stage isgreater than that of the reflecting surface 34Aa of the second auxiliaryreflector 34A positioned at the lowermost stage. Therefore, it ispossible to align the positions of the upper edges of the auxiliarylight distribution patterns PA, PB and PC formed by the lights reflectedfrom the second auxiliary reflectors 34A, 34B and 34C. Consequently, asynthetic light distribution pattern of the three auxiliary lightdistribution patterns PA, PB and PC can be formed as a lightdistribution pattern having a high contrast in an upper edge.

In the first exemplary embodiment, the reflecting surface 34Ca of thesecond auxiliary reflector 34C positioned at the uppermost stage isformed such that the light from the first auxiliary reflector 32 isreflected relatively upward on the left and right regions 34CaL and34CaR positioned on the respective sides of the central region 34CaC inthe right-and-left direction. Therefore, it is possible to align thepositions of the upper edges of the large light source image formed bythe light reflected from the central region 34CaC and the small lightsource image formed by the light reflected from each of the left andright regions 34CaL and 34CaR. Consequently, the auxiliary lightdistribution pattern PC formed by the light reflected from the secondauxiliary reflector 34C can be formed as a light distribution patternhaving a high contrast in the upper edge.

While description has been given on the assumption that the reflectingsurfaces 34Aa, 34Ba and 34Ca of the second auxiliary reflectors 34A, 34Band 34C are flat surfaces in the first exemplary embodiment, each of thereflecting surfaces 34Aa, 34Ba and 34Ca may be a curved surface in whicha downward inclination angle is gradually increased from a rear edgetoward a front edge. In such a case, it is possible to obtain thefollowing functions and advantages. More specifically, the spreading inthe vertical direction of the bundle of rays of the reflected light isslightly different between the vicinal regions of the rear edges andthose of the front edges of the reflecting surfaces 34Aa, 34Ba and 34Ca.Therefore, it is possible to increase the contrast of the upper edge ofthe auxiliary light distribution pattern PC still more by forming thereflecting surfaces 34Aa, 34Ba and 34Ca as the curved surfaces to causethe direction of the upper edge of the bundle of rays of the lightreflected by respective points on the reflecting surfaces 34Aa, 34Ba and34Ca to be coincident with a direction parallel to the optical axis Ax.In such a case, a degree of a curvature of the curved surface is verylow and a sectional shape taken along a vertical plane which is parallelto the optical axis Ax of each of the reflecting surfaces 34Aa, 34Ba and34Ca can be maintained to be a shape of an almost straight linedownwardly extending in the forward direction at a downward inclinationangle which is a little greater than a half of the downward inclinationangle of the axis line Ax2.

Next, description will be given to a second exemplary embodiment.

FIG. 6 illustrates a vehicle headlamp 110 according to the secondexemplary embodiment.

As shown in the drawing, the vehicle headlamp 110 according to thesecond exemplary embodiment has a basic structure which is the same asthat of the vehicle headlamp 10 according to the first exemplaryembodiment. However, the diffusion lens 40 according to the firstexemplary embodiment is not disposed, and furthermore, structures of afirst auxiliary reflector 132 and three second auxiliary reflectors134A, 134B and 134C are different from those of the first exemplaryembodiment.

More specifically, the second auxiliary reflectors 134A, 134B and 134Caccording to the second exemplary embodiment are disposed in front ofthe first auxiliary reflector 132 in the same manner as the secondauxiliary reflectors 34A, 34B and 34C of the first exemplary embodiment,and forwardly reflects a light emitted from a light source 14 a andreflected by the first auxiliary reflector 132. Reflecting surfaces134Aa, 134Ba and 134Ca of the second auxiliary reflectors 134A, 134B and134C are inclined flat surfaces having downward inclination angles whichare equal to those of the reflecting surfaces 34Aa, 34Ba and 34Ca of thesecond auxiliary reflectors 34A, 34B and 34C according to the firstexemplary embodiment.

A plurality of diffuse reflecting portions 134As, 134Bs and 134Cs, whichreflects a light reflected by the first auxiliary reflector 132 anddiffuses the light in a horizontal direction, is formed in shapes ofvertical stripes on the respective reflecting surfaces 134Aa, 134Ba and134Ca of the second auxiliary reflectors 134A, 134B and 134C.

Also in the second exemplary embodiment, the second auxiliary reflector134A positioned at the lowermost stage and the first auxiliary reflector132 are formed in a one-piece structure, and the other two secondauxiliary reflectors 134B and 134C are fixed to respective verticalwalls 132 b of the first auxiliary reflector 132 in both of left andright side edge portions.

Both of the vertical walls 132 b of the first auxiliary reflector 132are set to have a smaller longitudinal length than both of the verticalwalls 32 b of the first auxiliary reflector 32 of the first exemplaryembodiment in order to prevent a light diffused and reflected by each ofthe reflecting surfaces 134Aa, 134Ba and 134Ca from being shielded asgreatly as possible. The structure of the reflecting surface 132Aa ofthe first auxiliary reflector 132 is entirely the same as that of thereflecting surface 32Aa of the first auxiliary reflector 32 according tothe first exemplary embodiment.

Also in the case in which the vehicle headlamp 110 according to thesecond exemplary embodiment is employed, it is possible to form a lowbeam light distribution pattern which is almost the same as the low beamlight distribution pattern PL which is formed by the vehicle headlamp 10according to the first exemplary embodiment. In addition, in the vehicleheadlamp 110 according to the second exemplary embodiment, it ispossible to eliminate the diffusion lens 40.

While the description has been given on the assumption that the threesecond auxiliary reflectors 34A, 34B and 34C (or 134A, 134B and 134C)are disposed at almost equal intervals in the vertical direction in theexemplary embodiments, the intervals can also be set to be non-equal andthe number of the second auxiliary reflectors to be disposed can also beset to be two or at least four.

In the exemplary embodiments, description has been given on theassumption that the light source 14 a is disposed below the optical axisAx. As a matter of course, it is also possible to employ a structure inwhich the light source 14 a is disposed on the same level as the opticalaxis Ax.

The numeric values indicated as data in the exemplary embodiments areonly illustrative and it is a matter of course that they can be properlyset to be different values.

While description has been made in connection with exemplary embodimentsof the present invention, it will be obvious to those skilled in the artthat various changes and modification may be made therein withoutdeparting from the present invention. It is aimed, therefore, to coverin the appended claims all such changes and modifications falling withinthe true spirit and scope of the present invention.

1. A vehicle headlamp comprising: a projection lens disposed on anoptical axis extending in a longitudinal direction of a vehicle; a lightsource disposed on a rear side of a rear focal point of the projectionlens; a reflector which forwardly reflects a light emitted from thelight source toward the optical axis; a shade disposed such that anupper edge of the shade is positioned in the vicinity of the opticalaxis near the rear focal point, wherein the shade shields a part of thelight reflected by the reflector, and forms a cutoff line of a low beamlight distribution pattern; a first auxiliary reflector which isdisposed below the reflector, and downwardly reflects the light emittedfrom the light source in a forward direction; and a plurality of secondauxiliary reflectors which is disposed on a front side of the firstauxiliary reflector at a predetermined interval along a verticaldirection, and forwardly reflects the light reflected by the firstauxiliary reflector, wherein the light source is a line light sourceextending in a width direction of the vehicle, a sectional shape of areflecting surface of the first auxiliary reflector taken along avertical plane that is parallel to the optical axis is a shape of aparabola, the parabola having a focal point in the vicinity of the lightsource and an axis line downwardly extending in the forward direction ata predetermined downward inclination angle with respect to the opticalaxis, and a sectional shape of a reflecting surface of each of thesecond auxiliary reflectors taken along the vertical plane has a shapeof a substantially straight line downwardly extending in the forwarddirection at a downward inclination angle which is smaller than thepredetermined downward inclination angle.
 2. The vehicle headlampaccording to claim 1, wherein the projection lens is a Fresnel lens. 3.The vehicle headlamp according to claim 1, wherein the reflectingsurface of the first auxiliary reflector is formed in a shape of aparaboloid of revolution having the axis line downwardly extending inthe forward direction as a center axis thereof, and the reflectingsurface of each of the second auxiliary reflectors is flat.
 4. Thevehicle headlamp according to claims 1, wherein the sectional shape ofthe reflecting surface of the second auxiliary reflector disposed on anupper side has a larger downward inclination angle than the sectionalshape of the reflecting surface of the second auxiliary reflectordisposed on a lower side.
 5. The vehicle headlamp according to claim 1,wherein the reflecting surface of at least the second auxiliaryreflector disposed on an uppermost side is formed such that the lightreflected by the first auxiliary reflector is reflected more upwardly onrespective side regions in the width direction of the vehicle relativeto a central region.
 6. The vehicle headlamp according to claim 1,further comprising a diffusion lens disposed on a front side of thesecond auxiliary reflectors and which diffuses the light reflected bythe second auxiliary reflectors in the width direction of the vehicle.7. The vehicle headlamp according to claim 1, wherein the light sourceis disposed below the optical axis.
 8. The vehicle headlamp according toclaim 1, wherein the plurality of second auxiliary reflectors aredisposed at equal intervals along the vertical direction.
 9. The vehicleheadlamp according to claim 1, wherein the downward inclination angle ofthe substantially straight line downwardly extending in the forwarddirection is greater than one-half of the predetermined downwardinclination angle.
 10. The vehicle headlamp according to claim 1,wherein each of the second auxiliary reflectors includes a plurality ofdiffuse reflecting portions, wherein each of the diffuse reflectingportions reflects the light reflected by the first auxiliary reflectorand diffuses the light in the width direction of the vehicle.